Do Fat Teens Face an Early Death?

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Body mass index at adolescence is associated with all-cause mortality in adulthood.

In contrast to a documented decrease in mortality rates in normal weight participants, mortality rates among overweight and obese adolescents did not improve in the last 40 years.

Life expectancy gains seen over the last half-century do not appear to extend to adults who were overweight or obese in adolescence, according to a large study spanning several decades.

Overweight and obese teens in the study were more likely to die before reaching the age of 50 than their normal-weight peers, and the mortality trends of those born between 1970 and 1980 were no better than for those born decades earlier, Amir Tirosh, MD, PhD, of Harvard Medical School and Brigham and Women's Hospital, and colleagues wrote in the Journal of Clinical Endocrinology and Metabolism.

The findings, from an analysis that included more than 2 million Israelis followed from age 17 to age 50, may offer early warning of life expectancy reductions in the decades to come as a consequence of the obesity epidemic among children and teens.

"During the last 4 decades, a significant decrease in mortality rates was documented in normal-weight participants born between 1970 to 1980 versus those born between 1950 and 1960 (3.60/104 vs. 4.99/104 person-years, P<0.001). However, no improvement in survival rate was observed among overweight and obese adolescents during the same time interval." they wrote.

The study included 2.16 million Israeli adolescents (59.1% male), born between 1950 and 1993 who underwent compulsory medical evaluations for military service at age 17. Height and weight were measured and body mass index (BMI) was stratified based on CDC-established percentiles for age and sex.

The main outcome measure for the analysis was death before age 50, and Cox-proportional hazard models were used to assess mortality rates and trends over time. During 43,126,211 person-years of follow-up, 18,530 deaths were recorded.

Among the study findings:

As compared with rates observed in the 25th-50th BMI percentiles, all-cause mortality continuously increased across BMI range, reaching rates of 8.90/104 and 2.90/104 person-years for men and women with BMI>97th percentile, respectively.

A multivariate analysis adjusted for age, socioeconomic status, education, and ethnicity demonstrated a significant increase in mortality at BMI>50th percentile (BMI>20.55 kg/m2) for men and >85th percentile in women (BMI>24.78 kg/m2).

Among females, survival rates were significantly higher than males in all BMI categories, with men having about a 3-fold higher risk of dying before age 50 than women.

Adolescents between the 50th and 75th BMI percentiles had a 10% increase in death before age 50, while early mortality was more than two-fold higher for those who were obese, Tirosh said.

He added that while advances in medical care have dramatically reduced deaths from cardiovascular disease and diabetes over the last 4 decades, these advances do not appear to be impacting life expectancies among obese adolescents.

"The alarming conclusion from this study is that for unclear reasons, obese kids and adolescents have not benefited from the advances that have led to the improvements in mortality seen in the general population," Tirosh told MedPage Today.

The researchers did not have data on how the people in the study died, which they cited as a study limitation. They cited the large size of the study and the fact that they followed teens born over four decades as major strengths.

"You really need a cohort of 2 million people to address the issue of mortality at a young age," Tirosh said.

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